DE102006004191B4 - Deterministic communication system - Google Patents

Abstract

A method of controlling a communication system (1) for exchanging audio data between a plurality of subscribers, the communication system (1) comprising:
several system subscribers (T; T1, T2, T3) for buffering audio data,
a control bus (14) for the transmission of control commands to the system users (T; T1, T2, T3),
a data bus (12) for the output of audio data by the system subscribers (T; T1, T2, T3),
a central unit (10) retrieving from the plurality of system subscribers (T; T1, T2, T3) the audio data via the control bus (14) and receiving the audio data via the data bus (12),
characterized by the steps
during an initialization phase, checking the identity of the system subscribers (T; T1, T2, T3) by the central unit (10);
during a configuration phase, transmitting a predetermined data frame with a first synchronization signal (51), the user address (52) of a system user (T; T1, T2, T3), a payload data field (54) and a second synchronization signal ( 51) through the central unit (10) via the control bus ...

Description

The The invention relates to a deterministic communication system in particular for use in avionics systems.

The invention System can be used on aircraft of any kind, especially for airplanes and missiles. The Invention is generally applicable to Real-time applications are used, i. for systems operating under time conditions communicate and in which the achievement of the system functions depends on the timely exchange of data.

Out The prior art is conventional Ethernet connections known in which systems with decentralized or distributed modules used which have access to the Ethernet bus. Is known in In this context, the CSMA / CD (Carrier Sense multiple Access with Collision Detect). However, this system is unsuitable for real-time applications, because it can be self-blocking and not deterministic Behavior.

From the DE 34 24 866 C2 and the DE 34 26 893 A1 For example, a system is known which utilizes a common bus for all system subscribers in which the arrangement and number of time slots is configurable, after which access to system users and terminal units coupled to the bus is established is. In these systems, an initialization and request phase is initially provided, in which the required configuration of system participants is determined. This allows dynamic allocation of time windows for data transmission. A disadvantage of these systems is that waiting times arise, which is required for the data transmission, since each user unit is addressed individually and then reacts to it. The overall resulting wait time is composed of the response time for the user units and the length of the physical line dependent delay time of the data bus itself.

Further is from Hammond, Joseph L., O'Reilly, Peter J.P., "Performance Analysis of Local Computer Networks; Reading, Mass., USA, Addison-Wesley Publ. Company, Inc, 1986, pp. 193-198, ISBN 0-201-11530-1, a communication system known to the system subscriber at regular intervals through a central Computer to be queried. Such a "polling" system can be controlled so that the central computer addresses all participants individually ("roll-call"), or so that the central Computer addresses a first participant and this then the next participant etc. ("hub-mode").

Out US 2005/0144338 A1 discloses a data transmission device, in the case of a data transfer between a master device and several slave devices takes place. Here comes a procedure used, which relies on a double buffer while one usually works with simple buffers. During data transfer a first and a second buffer are used as converters or relays, where both buffers are used as data transfer transducers and the reading and writing of the data takes place simultaneously.

Out US 4,763,320 For example, a method and a device for transmitting digital data, in particular for aircraft, are known. In operation, a distinction is made between the following different transmission phases: an initialization phase in which all stations are polled by the central controller; a polling phase in which the individual stations access the bus; an assignment phase in which each station has a time window available for the polling response; a data phase in which data is transmitted. The central controller includes a phase controller, a request collector, a time window allocator, a register. Some stations are equipped with a query generator so that a demand can be displayed via the bus.

Out US 5,974,056 For example, a method and apparatus for transmitting data is known. The data may include voice data, signal data, flight control data, telephony data and other communication data. The data is transmitted in packets comprising a preamble, a header, data and / or signal data for transmission over a dual bus between preferably decentralized stations. The stations receive the data for transmission from connected peripheral devices such as microphones, speakers, etc., and the stations transmit the received data via these peripheral devices. The clock pulses of the station are synchronized with a synchronization signal originating from a master station. At each station one finds a device, eg a Manchester decoder, which recognizes the preambles which are shortened compared to Ethernet preambles, and this decoder is between the station's own data processing unit, eg a digital signal processor, a micro-controller, etc. and switched the bus.

Out EP 1 183 826 B1 are method and apparatus for periodic and aperiodic data transmission over an aircraft data bus be known. In a network therefor having a network data bus and a plurality of network interface control modules, at least one of the plurality of network interface control modules is arranged to act as a master time control NIC module in use. Periodic data is transmitted on the data bus in a first time interval and aperiodic data on the data bus at variable intervals. Based on priority, length and sequence of frames, it is determined which bandwidth is allocated to the aperiodic data transfers.

It The object of the invention is a deterministic communication system with one as possible low protocol overhead available close.

These Task is with the features of the independent claims 1 and 9 solved. further explanation are referenced in the on this dependent claims specified.

According to the invention is a Communication system with system participants and one connecting them Bus for exchanging data between the system participants as well a central unit for the configuration of communication between provided to the participants. The system participants stand by one Control bus and a data bus connected to the central unit. The central unit is the only one in the control bus connection Transmitter and in the data bus connection the only receiver, where also the control bus in addition Data to the system participants may contain. The bus access by the participants is by means of the central unit controlled, so the transmission from a subscriber via the data bus to the central unit and from there to the receiving system subscriber. In the central unit An exchange buffer is provided with which for data exchange between the participants a reflection of received data and a Passing on to the transmitting device of the central unit done can.

According to the invention is a digital communication system or avionics system with a central unit provided that as a master or a controller or a control unit for the Access through and exchange with other system modules. there becomes a time-slicing system used multiple participants by means of two separate Bus systems (time division multiplexed system with dual loop communication). This system can be based on a standard Ethernet configuration based.

There the inventive Kommunkations system using a deterministic bus access a central control unit has a relatively high reliability reachable.

The inventive system is in particular for transmission from tax or Switching signals and digitized analog signals, in particular for fast transmission of these signals, suitable.

The inventive system allows one advantageous organization of the data bus because of a modular System structure by means of two separate bus lines, both connected to the various system subscribers. A central unit uses a control bus as a control bus for transferring data only from the Central unit out to the participants. Submit the connected participants the data about one Data bus.

With the modular system structure according to the invention is achieved that an error in one of the connected participants the system not except Set function or block the entire data exchange.

The inventive system improves the bus concept by using two separate ones Bus lines, each with the different participants connected is. For transmission Data from the central unit is the one connected to it Control bus available. The transfer The data from the system participants to the central unit via the Data bus connecting the system participants with the central unit.

The inventive communication system or avionics system has a modular architecture in which a single system participant in an error, the data transfer not completely prevent or block. By using two separate Buses in the communication system can also use Ethernet components can be used, e.g. 10BASE-T: IEEE 802.3 Physical Layer Specification for a 10 Mb / s CSMA / CD local area network, IEEE 802.3 Clause 14 .; 100BASE-T: IEEE 802.3 Physical Layer specification for a 100 Mb / s CSMA / CD local area network, IEEE 802.3 Clause 22 and 28 .. An "Auto-Collision Detect" is no longer necessary when using a single bus system is not excluded can be.

The use of the dual bus system according to the invention has the advantage that a continuous data transmission from the central unit to the system users is ensured. Furthermore, a synchronous communication system is provided with simple means, the one multiple use of audio data transmission allowed.

in the The invention will be described with reference to the accompanying figures. Show it:

1 a schematic representation of an embodiment of the communication system according to the invention with a central unit and multiple participants and the dual bus system,

2 a functional representation of an embodiment of the in the communication system of 1 used central unit of the 1 .

3 a functional representation of an embodiment of the in the communication system of 1 used participants of the 1 .

4a a data set or data frame intended for the configuration phase for the transmission of data from the central unit to system subscribers,

4b a data word intended for the configuration phase or a data frame for the transmission of data from the central unit to system subscribers,

5a a data word intended for the payload phase or a data frame for the transmission of data from the central unit to system users,

5b a data word intended for the payload phase or a data frame for the transmission of data from system users to the central unit.

The communication system according to the invention 1 is in a functional representation of the 1 shown. A central unit 10 is on the one hand via a data bus 12 (Shared bus) with transmitting devices TX of system participants T functionally connected. Shown are three system participants T1, T2, T3. Furthermore, the central unit 10 on the other hand via a control bus 14 (Master bus) with receiving devices RX the coupled system participants T functionally connected. The central unit 10 is the only transmitter or transmitter in the control bus connection of the central unit with the subscribers T, that is, the subscribers T are merely passive receivers. The control bus 14 is intended for multiplex data transmission, that is to say for data transmission for different receivers or subscribers, bus access by the subscribers T from the central unit 10 is controlled.

In principle, functionally diverse subscribers can be used in the communication system. In special cases, equivalent subscribers T can also be used. The functional structure of an embodiment of a subscriber usable in the system according to the invention is shown in FIG 3 shown. The data sets or data frames supplied by the control bus and received by the receiver part RX in the subscriber T are processed in different modules according to the contents transmitted with the latter: in an address recognition module (address recognition) 21 , a Receive State Control Unit 22 , a master timer or a master clock 23 , in turn, with a loop counter 24 and a data input buffer (Data Input Buffer) 25 , The data input buffer 25 stands with an input-output interface 26 in connection with which the participant can in turn interact functionally with other systems or system modules. Through this interaction or through processing steps within the subscriber itself, data is sent to a data output buffer (Data Output Buffer). 27 via which the data to be transmitted can be sent to the transmitting device TX. The Receive State Control Unit 22 is with a transmission control unit (transmit control) 28 as well as with the input-output interface 26 and the loop counter 24 connected. The input-output interface 26 may include an A / D converter, speakers and other control devices.

The received data in each data frame or data frame (bus frame) is stored in the data input buffer (Data Input Buffer). 25 and the data to be transmitted for each data frame (bus frame) in the data output buffer (Data Output Buffer) 27 saved. The receiver part RX may be a master clock or a master time of the central unit 10 read and use. This regenerated time is given to the loop counter 24 supplied, the time for the next bus access of the relevant subscriber T as a function of the state variables of the receive state module (Receive State Control Unit) 22 sets.

When using Ethernet connections for the buses 12 . 14 For example, the receiver device RX can be based on the IEEE 802.3 standard

The central unit 10 includes a subscriber configuration control module 31 in which a list of the central unit 10 coupled part T is implemented. This list can be changed due to input data eg from a connected control unit such as a host controller or adapted to changed states. The Subscriber Configuration Control Module 31 stands with a data transfer memory (Transmitter Data Memory) 32 and this in turn with a transmission module 33 in connection. The Subscriber Configuration Control Module 31 Also determines what data from the data transfer memory (Transmitter Data Memory) 32 each in the transmission module 33 be pushed.

The transmission module 33 generates a complete data frame on the control bus 14 with a generally valid for the participants or controlling this synchronization signal. This is controlled or specified by a system time generator (System Clock Generator) 34 that with the transmission module 33 connected is.

• 1. eine Initialisierungs-Phase,
• 2. eine Konfigurations-Phase,
• 3. eine Nutzdaten-Phase.

A reception module 35 receives and controls the data received from the subscribers T and passes them to a receiver data memory (receiver data memory) 36 to, which has the function of a buffer. The receiver data memory (receiver data memory) 36 is a receiver data configuration module 39 assigned. In the case in which there is a communication connection between several subscribers T, the data can be exchanged via an exchange buffer (exchange buffer). 37 in the data transfer memory (Transmitter Data Memory) 32 be transmitted. The exchange buffer (Exchange Buffer) 37 is from a Data Switch Control Matrix 38 controlled or controlled. The different communication phases are from the control bus control unit 40 controlled, whereby the following three communication phases are defined:

• 1. an initialization phase,
• 2. a configuration phase,
• 3. a payload phase.

Thereby, the data capacity of each coupled to the bus system subscriber T can be adjusted and optimized. During the initialization phase, the central unit checks 10 which subscriber T has access to the bus at the current or at a given time and which data request (data demand) exists.

This can be done either by the central unit 10 itself or by collecting and prioritizing the requirements of the coupled subscriber T done.

Each data set (Data Frame) 50 in the bus transmission starts with a synchronization signal 51 , Preferably, this signal is equal to or corresponds in individual determination features of the protocol explanation for the higher-level synchronization of the protocol declaration according to the IEEE standard 802.3.

The synchronization signal 51 or the synchronization sequence comprises a "7 byte preamble" and a "start frame sequence" start sequence. The trailing end bits of the long ("11" according to IEEE 802.3) "Start Frame Sequence" is used for the exact higher-level synchronization (overall synchronization). To achieve a simple way of audio data transmission, the system audio sample time is related to the distance between two sync signals 51 and preferably set this equal. This means that the sample frequency of the connected analog-to-digital and digital-to-analog converters is distributed exactly over the entire system. Thus, all participants in the system 1 the same clock given.

The 4a . 4b show the data frames of the data bus 12 and the control bus 14 in the configuration phase. During the configuration phase transmits the central unit 10 a given data frame starting with the described synchronization sequence or the synchronization signal 51 , The synchronization signal 51 is used as control synchronization for the entire system. Furthermore, a Phase Lock Loop (PLL) according to the IEEE 802.3 standard is used to obtain accurate time information for all subscribers without requiring a separate line for transmitting time information or similar facilities. In this way it is also possible to synchronize the signal 51 , that is, its frequency or time frame, for the whole system to change. This allows the electromagnetic compatibility of the entire communication system 1 be improved.

The synchronization signal 51 is the subscriber address 52 of the subscriber T for whom the data to be transmitted are intended. The system 1 has specially reserved addresses that can not be assigned to real or physical subscribers T. These address words are used as Broadcast Addresses and the attached configuration data 53 determine the behavior of all connected participants T.

In this way, a predetermined amount of the payload data can be used eg for audio data that is continuously transmitted as a multi-channel transmission or multi-channel broadcast from the central unit 10 can be sent to the participants T. In a case where the address for a existing subscriber, affect the configuration data 53 the settings of the respective subscriber T. The payload attached to it 54 For example, they may contain audio data or circuit data for one unit (end unit).

Every data frame 50 is completed by an end sequence (check sequence) 55 for data validation, which can be eg a simple CRC check sequence.

The described data frame 50 will turn a sync signal 51 or a synchronization sequence 51 added. The corresponding audio sample time is given by the time from one end of a synchronization sequence 51 to the end of the next synchronization sequence 51 , An advantage of the solution according to the invention is that no waiting time or gaps are needed to order processes when different subscribers want to send T on the same line or bus.

During the configuration phase, the subscriber T responds by sending a simple data set or frame due to the receipt of his own address 60 over the data bus. This response is triggered by the address recognition module (Address Recognition) 21 , This data frame also starts with a synchronization sequence 51 , which is preferably based on the IEEE 802.3 standard, but this is not used for system synchronization. The structuring of the synchronization sequence 51 The IEEE 802.3 standard has the advantage that standard Ethernet modules and transceivers can be used. To the synchronization sequence 51 is the subscriber T an identification field (identifier field) 62 attached to the identification of the subscriber T, indicating the individual address of the subscriber T and the required amount of user data. Subsequently, the user data field 63 of the subscriber data frame and then a check sequence 64 attached for data validation.

After being sent by a subscriber T addresses the central unit 10 the same or a further subscriber T. During this time, no transmission takes place on the data bus until the next address is forwarded or recognized.

During the configuration phase sets the central unit 10 the order in which the subscribers T are addressed. This does not have to reflect the chronological order. As a result, each subscriber T stores an individual meter reading or an individual rank, which the subscriber T stores the configuration data 53 extracts.

The central unit 10 can then perform the payload phase via a specified subscriber address and a special configuration data field. This means that with the next synchronization sequence the loop counter 24 each participant T is started. Due to the count stored in each subscriber T, each subscriber T transmits his own data set or data frame to the data bus at a predetermined time. The order after which this transmission is made has been determined by the central unit 10 by means of the meter readings transmitted to the subscribers T.

As a result of this definition, all datasets or data frames are then in the subsequent user data transmission phase 70 . 80 , which are each sent from a subscriber T on the control bus and the data bus, different. Since the order of bus access is fixed, only the number determined by the central unit 10 transmitted synchronization signals bus access to the data bus. Thus, no overhead is required for the protocol within the records, so that almost all the access time to the bus is used for payload transfer ( 5a . 5b ).

The Invention may be IEEE 802.3 components (Physical Layer IEEE 802.3) for the Use data bus. The realization can be done by means of Ethernet components respectively.

For use of the invention in safety-critical systems, the control bus 14 redundant provided so be performed multiple times.

to fast audio data transmission can control clock recovery (master clock recovery) be implemented by integrated standard PLLS (according to IEEE 802.3 standard).

The data exchange between the system 1 coupled participants T can be done with scalable data sizes.

The data exchange between subscribers T can be done simply by mirroring the data in the exchange buffer 37 (exchange buffer) due to a deterministic triggered protocol.

Claims (13)

Method for controlling a communication system ( 1 ) for exchanging audio data between a plurality of subscribers, the communication system ( 1 ) comprises: a plurality of system subscribers (T; T1, T2, T3) for one Caching of audio data, a control bus ( 14 ) for the transmission of control commands to the system subscribers (T; T1, T2, T3), a data bus ( 12 ) for the output of audio data by the system subscribers (T; T1, T2, T3), a central unit ( 10 ) of the several system subscribers (T; T1, T2, T3), the audio data via the control bus ( 14 ) and retrieves the audio data via the data bus ( 12 ), characterized by the steps during an initialization phase, checking the identity of the system subscribers (T; T1, T2, T3) by the central unit ( 10 ); during a configuration phase, transmitting a given data frame with a first synchronization signal ( 51 ), the participant's address ( 52 ) of a system user (T; T1, T2, T3), a payload field ( 54 ) and a second synchronization signal ( 51 ) by the central unit ( 10 ) via the control bus ( 14 ); during a payload phase, transfer of audio data records by a system subscriber (T; T1, T2, T3) via the data bus ( 12 ) in an audio sample time corresponding to the period between the first sync signal and the second sync signal. Method according to claim 1, characterized in that the system user (T; T1, T2, T3) recognizes his own address during the configuration phase a data frame ( 60 ) over the data bus ( 12 ). Method according to Claim 1, characterized in that the sending of a data record by each system subscriber (T; T1, T2, T3) takes place on the data bus at a predetermined point in time ( 12 ) carried out by the central unit ( 10 ). Method according to Claim 1, characterized in that the order of transmission by the system users (T; T1, T2, T3) during the payload data phase is determined by the central unit (T; 10 ) is determined in advance. Method according to one of the preceding claims, characterized in that the synchronization signal ( 51 ) from a system time generator ( 34 ) is produced. Method according to one of the preceding claims, characterized in that the synchronization signal ( 51 ) is a signal according to the IEEE standard 802.3. Method according to one of the preceding claims, characterized in that from the system users (T; T1, T2, T3) a clock recovery from the synchronization signal (T; 51 ) is performed with a phase locked loop (PLL). Method according to one of the preceding claims, characterized in that a data exchange between system users (T; T1, T2, T3) by mirroring of the data in an exchange buffer ( 37 ) of the central unit ( 10 ) he follows. Communication system ( 1 ) for exchanging audio data between a plurality of subscribers, comprising: a plurality of system subscribers (T; T1, T2, T3) for buffering audio data, a control bus ( 14 ) for the transmission of control commands to the system subscribers (T; T1, T2, T3), a data bus ( 12 ) for the output of audio data by the system subscribers (T; T1, T2, T3), a central unit ( 10 ) of the several system subscribers (T; T1, T2, T3), the audio data via the control bus ( 14 ) and retrieves the audio data via the data bus ( 12 ), characterized in that during an initialization phase the central unit ( 10 ) verifies the identity of the system subscribers (T; T1, T2, T3); during a configuration phase through the central unit ( 10 ) via the control bus ( 14 ) a predetermined data frame with a first synchronization signal ( 51 ), the participant's address ( 52 ) of a system user (T; T1, T2, T3), a payload field ( 54 ) and a second synchronization signal ( 51 ) is transmitted; during a payload phase, audio data sets through a system subscriber (T; T1, T2, T3) via the data bus (FIG. 12 ) during an audio sample time corresponding to the time period between the first sync signal and the second sync signal. Communication system ( 1 ) according to claim 9, characterized in that the central unit ( 10 ) a subscriber configuration control module ( 31 ) comprising a list of the system subscribers (T; T1, T2, T3). Communication system ( 1 ) according to claim 10, characterized in that the subscriber configuration control module ( 31 ) with a transmission module ( 33 ) is connected to generate the data frame. Communication system ( 1 ) according to one of claims 9 to 11, characterized in that the system users (T; T1, T2, T3) each comprise a phase-locked loop for clock recovery from the synchronization signal (T; 51 ). Communication system ( 1 ) according to one of claims 9 to 12, characterized in that in the central unit ( 10 ) an exchange buffer ( 37 ) is provided, with the data exchange between the participants, a mirroring of received data and forwarding to the transmitting device of the central unit ( 10 ).